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AUDIO INTEGRATING - DESCRIPTION AND OPERATION
1. General
A. The flight interphone system and audio selecting system provide the connecting link between the airplane radio receivers, transmitters, and interphone systems. Audio selector panels and associated headphones and microphones enable control cabin crewmembers to complete voice communications over the HF (if installed) and VHF communication, interphone, and passenger address systems. The ADF, DME, marker beacon, and VOR (VHF) navigation receivers may also be monitored.
B. The flight interphone system enables control cabin members to communicate with each other with their associated microphones, headphones and audio selector panels. An interphone amplifier provides the necessary audio amplification between stations. The amplifier is in the audio accessory unit. Two loudspeakers installed in the control cabin enable the captain and first officer to monitor systems selected on their audio selector panels without wearing headphones. The captain and first officer have INT-MIC PTT switches on their respective control wheels which may be used with oxygen mask microphones or boom microphones to complete communications to selected systems or directly to the interphone system. An earphone/boom microphone headset and oxygen mask microphone are provided at the captain's and first officer's stations. A headphone, handheld microphone, and oxygen mask microphone are provided at the observer's station. A flight interphone handset jack is on external ground power receptacle panel P19.
C. The audio selecting system consists of audio selector panels which enable crewmembers to select any of the airplane communication facilities. Audio selector panels are located at the captain's, first officer's, and observer's stations. Audio selector panel circuits are paralleled on electronic rack shelf E2-1.
D. The audio selector panels, loudspeakers and interphone amplifier use 28 volts dc obtained from the battery bus and unswitched electronics bus No. 2. Systems circuit breakers are on load control center P6.
E. Pressing a push-to-talk button when a radio system has been selected on an associated audio selector panel will cause an event marker to be recorded by the flight data recorder (Ref Chapter 31, Flight Recorder System).
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FLIGHT INTERPHONE SYSTEM - DESCRIPTION AND OPERATION
EFFECTIVITY
Airplanes without Digital Flight Interphone
1. General
A. The flight interphone system allows the crewmembers to communicate with each other or ground facilities. Audio selector panels enable crewmembers to select and complete voice communications over the selected system. Refer to 23-53-0 for audio selector panels.
B. The flight interphone system consists of a flight interphone amplifier, oxygen mask and handheld microphones, headphones, boom mike/headphone headsets, and two loudspeakers. The amplifier is installed as a module in the audio accessory unit on electronics rack E2-1. The flight interphone amplifier gain potentiometer is mounted on the front of the accessory unit. The captain and first officer each have a loudspeaker assembly installed in the ceiling panels at their stations. A flight interphone handset jack on external ground power receptacle panel P19 is paralleled to the flight interphone amplifier for communications between ground personnel and crewmembers (Fig. 1).
C. The captain and first officer each have boom mike/headphone, oxygen mask microphone, handheld microphone, and headphone jacks installed on the sidewalls of their stations. Oxygen mask and boom microphone INT-MIC push-to-talk (PTT) switches are on the outboard horn of their control wheels. An oxygen mask and boom microphone PTT button is on each of their audio selector panels (Fig. 1).
D. Headphone, handheld microphone, and oxygen mask microphone jacks are installed at the first observer's station. A headphone jack for a second observer is provided and is paralleled to the first observer's headphone jack inside the first observer's audio selector panel. An oxygen mask and boom microphone PTT button is on the first observer's audio selector panel (Fig. 1).
E. The flight interphone amplifier and loudspeaker assemblies use a 28-volt dc dual power source from the battery bus and unswitched electronics bus No. 2. Circuit breakers are on load control center P6. The loudspeaker assemblies use 28 volts dc from the same circuit breakers that supply power for the audio selector panels (Fig. 2).
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